[PATCH v4 0/9] vdpa_sim: add support for user VA

[PATCH v4 0/9] vdpa_sim: add support for user VA

[Stefano Garzarella]

This series adds support for the use of user virtual addresses in the
vDPA simulator devices.

The main reason for this change is to lift the pinning of all guest memory.
Especially with virtio devices implemented in software.

The next step would be to generalize the code in vdpa-sim to allow the
implementation of in-kernel software devices. Similar to vhost, but using vDPA
so we can reuse the same software stack (e.g. in QEMU) for both HW and SW
devices.

For example, we have never merged vhost-blk, and lately there has been interest.
So it would be nice to do it directly with vDPA to reuse the same code in the
VMM for both HW and SW vDPA block devices.

The main problem (addressed by this series) was due to the pinning of all
guest memory, which thus prevented the overcommit of guest memory.

Thanks,
Stefano

Changelog listed in each patch.
v3: https://lore.kernel.org/lkml/20230321154228.182769-1-sgarzare@redhat.com/
v2: https://lore.kernel.org/lkml/20230302113421.174582-1-sgarzare@redhat.com/
RFC v1: https://lore.kernel.org/lkml/20221214163025.103075-1-sgarzare@redhat.com/

Stefano Garzarella (9):
  vdpa: add bind_mm/unbind_mm callbacks
  vhost-vdpa: use bind_mm/unbind_mm device callbacks
  vringh: replace kmap_atomic() with kmap_local_page()
  vringh: define the stride used for translation
  vringh: support VA with iotlb
  vdpa_sim: make devices agnostic for work management
  vdpa_sim: use kthread worker
  vdpa_sim: replace the spinlock with a mutex to protect the state
  vdpa_sim: add support for user VA

 drivers/vdpa/vdpa_sim/vdpa_sim.h     |  11 +-
 include/linux/vdpa.h                 |  10 ++
 include/linux/vringh.h               |   9 ++
 drivers/vdpa/vdpa_sim/vdpa_sim.c     | 161 ++++++++++++++++++++-----
 drivers/vdpa/vdpa_sim/vdpa_sim_blk.c |  10 +-
 drivers/vdpa/vdpa_sim/vdpa_sim_net.c |  10 +-
 drivers/vhost/vdpa.c                 |  34 ++++++
 drivers/vhost/vringh.c               | 173 ++++++++++++++++++++++-----
 8 files changed, 340 insertions(+), 78 deletions(-)

-- 
2.39.2

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[PATCH v4 1/9] vdpa: add bind_mm/unbind_mm callbacks

[Stefano Garzarella]

These new optional callbacks is used to bind/unbind the device to
a specific address space so the vDPA framework can use VA when
these callbacks are implemented.

Suggested-by: Jason Wang <jasowang@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---

Notes:
    v2:
    - removed `struct task_struct *owner` param (unused for now, maybe
      useful to support cgroups) [Jason]
    - add unbind_mm callback [Jason]

 include/linux/vdpa.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
index 43f59ef10cc9..369c21394284 100644
--- a/include/linux/vdpa.h
+++ b/include/linux/vdpa.h
@@ -290,6 +290,14 @@ struct vdpa_map_file {
  *				@vdev: vdpa device
  *				@idx: virtqueue index
  *				Returns pointer to structure device or error (NULL)
+ * @bind_mm:			Bind the device to a specific address space
+ *				so the vDPA framework can use VA when this
+ *				callback is implemented. (optional)
+ *				@vdev: vdpa device
+ *				@mm: address space to bind
+ * @unbind_mm:			Unbind the device from the address space
+ *				bound using the bind_mm callback. (optional)
+ *				@vdev: vdpa device
  * @free:			Free resources that belongs to vDPA (optional)
  *				@vdev: vdpa device
  */
@@ -351,6 +359,8 @@ struct vdpa_config_ops {
 	int (*set_group_asid)(struct vdpa_device *vdev, unsigned int group,
 			      unsigned int asid);
 	struct device *(*get_vq_dma_dev)(struct vdpa_device *vdev, u16 idx);
+	int (*bind_mm)(struct vdpa_device *vdev, struct mm_struct *mm);
+	void (*unbind_mm)(struct vdpa_device *vdev);
 
 	/* Free device resources */
 	void (*free)(struct vdpa_device *vdev);
-- 
2.39.2

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[PATCH v4 2/9] vhost-vdpa: use bind_mm/unbind_mm device callbacks

[Stefano Garzarella]

When the user call VHOST_SET_OWNER ioctl and the vDPA device
has `use_va` set to true, let's call the bind_mm callback.
In this way we can bind the device to the user address space
and directly use the user VA.

The unbind_mm callback is called during the release after
stopping the device.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---

Notes:
    v4:
    - added new switch after vhost_dev_ioctl() [Jason]
    v3:
    - added `case VHOST_SET_OWNER` in vhost_vdpa_unlocked_ioctl() [Jason]
    v2:
    - call the new unbind_mm callback during the release [Jason]
    - avoid to call bind_mm callback after the reset, since the device
      is not detaching it now during the reset

 drivers/vhost/vdpa.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 7be9d9d8f01c..3824c249612f 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -219,6 +219,28 @@ static int vhost_vdpa_reset(struct vhost_vdpa *v)
 	return vdpa_reset(vdpa);
 }
 
+static long vhost_vdpa_bind_mm(struct vhost_vdpa *v)
+{
+	struct vdpa_device *vdpa = v->vdpa;
+	const struct vdpa_config_ops *ops = vdpa->config;
+
+	if (!vdpa->use_va || !ops->bind_mm)
+		return 0;
+
+	return ops->bind_mm(vdpa, v->vdev.mm);
+}
+
+static void vhost_vdpa_unbind_mm(struct vhost_vdpa *v)
+{
+	struct vdpa_device *vdpa = v->vdpa;
+	const struct vdpa_config_ops *ops = vdpa->config;
+
+	if (!vdpa->use_va || !ops->unbind_mm)
+		return;
+
+	ops->unbind_mm(vdpa);
+}
+
 static long vhost_vdpa_get_device_id(struct vhost_vdpa *v, u8 __user *argp)
 {
 	struct vdpa_device *vdpa = v->vdpa;
@@ -716,6 +738,17 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
 		break;
 	}
 
+	if (r)
+		goto out;
+
+	switch (cmd) {
+	case VHOST_SET_OWNER:
+		r = vhost_vdpa_bind_mm(v);
+		if (r)
+			vhost_dev_reset_owner(d, NULL);
+		break;
+	}
+out:
 	mutex_unlock(&d->mutex);
 	return r;
 }
@@ -1287,6 +1320,7 @@ static int vhost_vdpa_release(struct inode *inode, struct file *filep)
 	vhost_vdpa_clean_irq(v);
 	vhost_vdpa_reset(v);
 	vhost_dev_stop(&v->vdev);
+	vhost_vdpa_unbind_mm(v);
 	vhost_vdpa_config_put(v);
 	vhost_vdpa_cleanup(v);
 	mutex_unlock(&d->mutex);
-- 
2.39.2

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[PATCH v4 3/9] vringh: replace kmap_atomic() with kmap_local_page()

[Stefano Garzarella]

kmap_atomic() is deprecated in favor of kmap_local_page() since commit
f3ba3c710ac5 ("mm/highmem: Provide kmap_local*").

With kmap_local_page() the mappings are per thread, CPU local, can take
page-faults, and can be called from any context (including interrupts).
Furthermore, the tasks can be preempted and, when they are scheduled to
run again, the kernel virtual addresses are restored and still valid.

kmap_atomic() is implemented like a kmap_local_page() which also disables
page-faults and preemption (the latter only for !PREEMPT_RT kernels,
otherwise it only disables migration).

The code within the mappings/un-mappings in getu16_iotlb() and
putu16_iotlb() don't depend on the above-mentioned side effects of
kmap_atomic(), so that mere replacements of the old API with the new one
is all that is required (i.e., there is no need to explicitly add calls
to pagefault_disable() and/or preempt_disable()).

This commit reuses a "boiler plate" commit message from Fabio, who has
already did this change in several places.

Cc: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
Reviewed-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---

Notes:
    v3:
    - credited Fabio for the commit message
    - added reference to the commit that deprecated kmap_atomic() [Jason]
    v2:
    - added this patch since checkpatch.pl complained about deprecation
      of kmap_atomic() touched by next patch

 drivers/vhost/vringh.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index a1e27da54481..0ba3ef809e48 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -1220,10 +1220,10 @@ static inline int getu16_iotlb(const struct vringh *vrh,
 	if (ret < 0)
 		return ret;
 
-	kaddr = kmap_atomic(iov.bv_page);
+	kaddr = kmap_local_page(iov.bv_page);
 	from = kaddr + iov.bv_offset;
 	*val = vringh16_to_cpu(vrh, READ_ONCE(*(__virtio16 *)from));
-	kunmap_atomic(kaddr);
+	kunmap_local(kaddr);
 
 	return 0;
 }
@@ -1241,10 +1241,10 @@ static inline int putu16_iotlb(const struct vringh *vrh,
 	if (ret < 0)
 		return ret;
 
-	kaddr = kmap_atomic(iov.bv_page);
+	kaddr = kmap_local_page(iov.bv_page);
 	to = kaddr + iov.bv_offset;
 	WRITE_ONCE(*(__virtio16 *)to, cpu_to_vringh16(vrh, val));
-	kunmap_atomic(kaddr);
+	kunmap_local(kaddr);
 
 	return 0;
 }
-- 
2.39.2

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[PATCH v4 4/9] vringh: define the stride used for translation

[Stefano Garzarella]

Define a macro to be reused in the different parts of the code.

Useful for the next patches where we add more arrays to manage also
translations with user VA.

Suggested-by: Eugenio Perez Martin <eperezma@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---

Notes:
    v4:
    - added this patch with the changes extracted from the next patch [Eugenio]
    - used _STRIDE instead of _SIZE [Eugenio]

 drivers/vhost/vringh.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index 0ba3ef809e48..4aee230f7622 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -1141,13 +1141,15 @@ static int iotlb_translate(const struct vringh *vrh,
 	return ret;
 }
 
+#define IOTLB_IOV_STRIDE 16
+
 static inline int copy_from_iotlb(const struct vringh *vrh, void *dst,
 				  void *src, size_t len)
 {
 	u64 total_translated = 0;
 
 	while (total_translated < len) {
-		struct bio_vec iov[16];
+		struct bio_vec iov[IOTLB_IOV_STRIDE];
 		struct iov_iter iter;
 		u64 translated;
 		int ret;
@@ -1180,7 +1182,7 @@ static inline int copy_to_iotlb(const struct vringh *vrh, void *dst,
 	u64 total_translated = 0;
 
 	while (total_translated < len) {
-		struct bio_vec iov[16];
+		struct bio_vec iov[IOTLB_IOV_STRIDE];
 		struct iov_iter iter;
 		u64 translated;
 		int ret;
-- 
2.39.2

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[PATCH v4 5/9] vringh: support VA with iotlb

[Stefano Garzarella]

vDPA supports the possibility to use user VA in the iotlb messages.
So, let's add support for user VA in vringh to use it in the vDPA
simulators.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---

Notes:
    v4:
    - used uintptr_t for `io_addr` [Eugenio]
    - added `io_addr` and `io_len` variables in iotlb_translate
    - avoided overflow doing `map->addr - map->start + addr` [Jason]
    - removed `is_iovec` field from struct iotlb_vec [Jason]
    - added vringh_init_iotlb_va() [Jason]
    v3:
    - refactored avoiding code duplication [Eugenio]
    v2:
    - replace kmap_atomic() with kmap_local_page() [see previous patch]
    - fix cast warnings when build with W=1 C=1

 include/linux/vringh.h |   9 +++
 drivers/vhost/vringh.c | 171 +++++++++++++++++++++++++++++++++--------
 2 files changed, 148 insertions(+), 32 deletions(-)

diff --git a/include/linux/vringh.h b/include/linux/vringh.h
index 1991a02c6431..b4edfadf5479 100644
--- a/include/linux/vringh.h
+++ b/include/linux/vringh.h
@@ -32,6 +32,9 @@ struct vringh {
 	/* Can we get away with weak barriers? */
 	bool weak_barriers;
 
+	/* Use user's VA */
+	bool use_va;
+
 	/* Last available index we saw (ie. where we're up to). */
 	u16 last_avail_idx;
 
@@ -284,6 +287,12 @@ int vringh_init_iotlb(struct vringh *vrh, u64 features,
 		      struct vring_avail *avail,
 		      struct vring_used *used);
 
+int vringh_init_iotlb_va(struct vringh *vrh, u64 features,
+			 unsigned int num, bool weak_barriers,
+			 struct vring_desc *desc,
+			 struct vring_avail *avail,
+			 struct vring_used *used);
+
 int vringh_getdesc_iotlb(struct vringh *vrh,
 			 struct vringh_kiov *riov,
 			 struct vringh_kiov *wiov,
diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index 4aee230f7622..771c2aba8aac 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -1094,10 +1094,17 @@ EXPORT_SYMBOL(vringh_need_notify_kern);
 
 #if IS_REACHABLE(CONFIG_VHOST_IOTLB)
 
+struct iotlb_vec {
+	union {
+		struct iovec *iovec;
+		struct bio_vec *bvec;
+	} iov;
+	size_t count;
+};
+
 static int iotlb_translate(const struct vringh *vrh,
 			   u64 addr, u64 len, u64 *translated,
-			   struct bio_vec iov[],
-			   int iov_size, u32 perm)
+			   struct iotlb_vec *ivec, u32 perm)
 {
 	struct vhost_iotlb_map *map;
 	struct vhost_iotlb *iotlb = vrh->iotlb;
@@ -1107,9 +1114,11 @@ static int iotlb_translate(const struct vringh *vrh,
 	spin_lock(vrh->iotlb_lock);
 
 	while (len > s) {
-		u64 size, pa, pfn;
+		uintptr_t io_addr;
+		size_t io_len;
+		u64 size;
 
-		if (unlikely(ret >= iov_size)) {
+		if (unlikely(ret >= ivec->count)) {
 			ret = -ENOBUFS;
 			break;
 		}
@@ -1124,10 +1133,22 @@ static int iotlb_translate(const struct vringh *vrh,
 		}
 
 		size = map->size - addr + map->start;
-		pa = map->addr + addr - map->start;
-		pfn = pa >> PAGE_SHIFT;
-		bvec_set_page(&iov[ret], pfn_to_page(pfn), min(len - s, size),
-			      pa & (PAGE_SIZE - 1));
+		io_len = min(len - s, size);
+		io_addr = map->addr - map->start + addr;
+
+		if (vrh->use_va) {
+			struct iovec *iovec = ivec->iov.iovec;
+
+			iovec[ret].iov_len = io_len;
+			iovec[ret].iov_base = (void __user *)io_addr;
+		} else {
+			u64 pfn = io_addr >> PAGE_SHIFT;
+			struct bio_vec *bvec = ivec->iov.bvec;
+
+			bvec_set_page(&bvec[ret], pfn_to_page(pfn), io_len,
+				      io_addr & (PAGE_SIZE - 1));
+		}
+
 		s += size;
 		addr += size;
 		++ret;
@@ -1146,23 +1167,36 @@ static int iotlb_translate(const struct vringh *vrh,
 static inline int copy_from_iotlb(const struct vringh *vrh, void *dst,
 				  void *src, size_t len)
 {
+	struct iotlb_vec ivec;
+	union {
+		struct iovec iovec[IOTLB_IOV_STRIDE];
+		struct bio_vec bvec[IOTLB_IOV_STRIDE];
+	} iov;
 	u64 total_translated = 0;
 
+	ivec.iov.iovec = iov.iovec;
+	ivec.count = IOTLB_IOV_STRIDE;
+
 	while (total_translated < len) {
-		struct bio_vec iov[IOTLB_IOV_STRIDE];
 		struct iov_iter iter;
 		u64 translated;
 		int ret;
 
 		ret = iotlb_translate(vrh, (u64)(uintptr_t)src,
 				      len - total_translated, &translated,
-				      iov, ARRAY_SIZE(iov), VHOST_MAP_RO);
+				      &ivec, VHOST_MAP_RO);
 		if (ret == -ENOBUFS)
-			ret = ARRAY_SIZE(iov);
+			ret = IOTLB_IOV_STRIDE;
 		else if (ret < 0)
 			return ret;
 
-		iov_iter_bvec(&iter, ITER_SOURCE, iov, ret, translated);
+		if (vrh->use_va) {
+			iov_iter_init(&iter, ITER_SOURCE, ivec.iov.iovec, ret,
+				      translated);
+		} else {
+			iov_iter_bvec(&iter, ITER_SOURCE, ivec.iov.bvec, ret,
+				      translated);
+		}
 
 		ret = copy_from_iter(dst, translated, &iter);
 		if (ret < 0)
@@ -1179,23 +1213,36 @@ static inline int copy_from_iotlb(const struct vringh *vrh, void *dst,
 static inline int copy_to_iotlb(const struct vringh *vrh, void *dst,
 				void *src, size_t len)
 {
+	struct iotlb_vec ivec;
+	union {
+		struct iovec iovec[IOTLB_IOV_STRIDE];
+		struct bio_vec bvec[IOTLB_IOV_STRIDE];
+	} iov;
 	u64 total_translated = 0;
 
+	ivec.iov.iovec = iov.iovec;
+	ivec.count = IOTLB_IOV_STRIDE;
+
 	while (total_translated < len) {
-		struct bio_vec iov[IOTLB_IOV_STRIDE];
 		struct iov_iter iter;
 		u64 translated;
 		int ret;
 
 		ret = iotlb_translate(vrh, (u64)(uintptr_t)dst,
 				      len - total_translated, &translated,
-				      iov, ARRAY_SIZE(iov), VHOST_MAP_WO);
+				      &ivec, VHOST_MAP_WO);
 		if (ret == -ENOBUFS)
-			ret = ARRAY_SIZE(iov);
+			ret = IOTLB_IOV_STRIDE;
 		else if (ret < 0)
 			return ret;
 
-		iov_iter_bvec(&iter, ITER_DEST, iov, ret, translated);
+		if (vrh->use_va) {
+			iov_iter_init(&iter, ITER_DEST, ivec.iov.iovec, ret,
+				      translated);
+		} else {
+			iov_iter_bvec(&iter, ITER_DEST, ivec.iov.bvec, ret,
+				      translated);
+		}
 
 		ret = copy_to_iter(src, translated, &iter);
 		if (ret < 0)
@@ -1212,20 +1259,36 @@ static inline int copy_to_iotlb(const struct vringh *vrh, void *dst,
 static inline int getu16_iotlb(const struct vringh *vrh,
 			       u16 *val, const __virtio16 *p)
 {
-	struct bio_vec iov;
-	void *kaddr, *from;
+	struct iotlb_vec ivec;
+	union {
+		struct iovec iovec[1];
+		struct bio_vec bvec[1];
+	} iov;
+	__virtio16 tmp;
 	int ret;
 
+	ivec.iov.iovec = iov.iovec;
+	ivec.count = 1;
+
 	/* Atomic read is needed for getu16 */
-	ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p), NULL,
-			      &iov, 1, VHOST_MAP_RO);
+	ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p),
+			      NULL, &ivec, VHOST_MAP_RO);
 	if (ret < 0)
 		return ret;
 
-	kaddr = kmap_local_page(iov.bv_page);
-	from = kaddr + iov.bv_offset;
-	*val = vringh16_to_cpu(vrh, READ_ONCE(*(__virtio16 *)from));
-	kunmap_local(kaddr);
+	if (vrh->use_va) {
+		ret = __get_user(tmp, (__virtio16 __user *)ivec.iov.iovec[0].iov_base);
+		if (ret)
+			return ret;
+	} else {
+		void *kaddr = kmap_local_page(ivec.iov.bvec[0].bv_page);
+		void *from = kaddr + ivec.iov.bvec[0].bv_offset;
+
+		tmp = READ_ONCE(*(__virtio16 *)from);
+		kunmap_local(kaddr);
+	}
+
+	*val = vringh16_to_cpu(vrh, tmp);
 
 	return 0;
 }
@@ -1233,20 +1296,36 @@ static inline int getu16_iotlb(const struct vringh *vrh,
 static inline int putu16_iotlb(const struct vringh *vrh,
 			       __virtio16 *p, u16 val)
 {
-	struct bio_vec iov;
-	void *kaddr, *to;
+	struct iotlb_vec ivec;
+	union {
+		struct iovec iovec;
+		struct bio_vec bvec;
+	} iov;
+	__virtio16 tmp;
 	int ret;
 
+	ivec.iov.iovec = &iov.iovec;
+	ivec.count = 1;
+
 	/* Atomic write is needed for putu16 */
-	ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p), NULL,
-			      &iov, 1, VHOST_MAP_WO);
+	ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p),
+			      NULL, &ivec, VHOST_MAP_RO);
 	if (ret < 0)
 		return ret;
 
-	kaddr = kmap_local_page(iov.bv_page);
-	to = kaddr + iov.bv_offset;
-	WRITE_ONCE(*(__virtio16 *)to, cpu_to_vringh16(vrh, val));
-	kunmap_local(kaddr);
+	tmp = cpu_to_vringh16(vrh, val);
+
+	if (vrh->use_va) {
+		ret = __put_user(tmp, (__virtio16 __user *)ivec.iov.iovec[0].iov_base);
+		if (ret)
+			return ret;
+	} else {
+		void *kaddr = kmap_local_page(ivec.iov.bvec[0].bv_page);
+		void *to = kaddr + ivec.iov.bvec[0].bv_offset;
+
+		WRITE_ONCE(*(__virtio16 *)to, tmp);
+		kunmap_local(kaddr);
+	}
 
 	return 0;
 }
@@ -1320,11 +1399,39 @@ int vringh_init_iotlb(struct vringh *vrh, u64 features,
 		      struct vring_avail *avail,
 		      struct vring_used *used)
 {
+	vrh->use_va = false;
+
 	return vringh_init_kern(vrh, features, num, weak_barriers,
 				desc, avail, used);
 }
 EXPORT_SYMBOL(vringh_init_iotlb);
 
+/**
+ * vringh_init_iotlb_va - initialize a vringh for a ring with IOTLB containing
+ *                        user VA.
+ * @vrh: the vringh to initialize.
+ * @features: the feature bits for this ring.
+ * @num: the number of elements.
+ * @weak_barriers: true if we only need memory barriers, not I/O.
+ * @desc: the userpace descriptor pointer.
+ * @avail: the userpace avail pointer.
+ * @used: the userpace used pointer.
+ *
+ * Returns an error if num is invalid.
+ */
+int vringh_init_iotlb_va(struct vringh *vrh, u64 features,
+			 unsigned int num, bool weak_barriers,
+			 struct vring_desc *desc,
+			 struct vring_avail *avail,
+			 struct vring_used *used)
+{
+	vrh->use_va = true;
+
+	return vringh_init_kern(vrh, features, num, weak_barriers,
+				desc, avail, used);
+}
+EXPORT_SYMBOL(vringh_init_iotlb_va);
+
 /**
  * vringh_set_iotlb - initialize a vringh for a ring with IOTLB.
  * @vrh: the vring
-- 
2.39.2

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Re: [PATCH v4 5/9] vringh: support VA with iotlb

[Stefano Garzarella]

On Thu, Mar 30, 2023 at 03:02:21PM +0200, Simon Horman wrote:
>On Fri, Mar 24, 2023 at 04:39:19PM +0100, Stefano Garzarella wrote:
>> vDPA supports the possibility to use user VA in the iotlb messages.
>> So, let's add support for user VA in vringh to use it in the vDPA
>> simulators.
>>
>> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
>
>...
>
>> +/**
>> + * vringh_init_iotlb_va - initialize a vringh for a ring with IOTLB containing
>> + *                        user VA.
>> + * @vrh: the vringh to initialize.
>> + * @features: the feature bits for this ring.
>> + * @num: the number of elements.
>> + * @weak_barriers: true if we only need memory barriers, not I/O.
>> + * @desc: the userpace descriptor pointer.
>> + * @avail: the userpace avail pointer.
>> + * @used: the userpace used pointer.
>
>nit: s/userpace/userspace/

Oops, good catch!

Copy & past typos also present in the documentation of vringh_init_kern
and vringh_init_iotlb.

I will fix this patch and send a separate patch to fix the other two.

Thanks,
Stefano

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[PATCH v4 6/9] vdpa_sim: make devices agnostic for work management

[Stefano Garzarella]

[-- Attachment #1: Type: text/plain, Size: 5215 bytes --]

Let's move work management inside the vdpa_sim core.
This way we can easily change how we manage the works, without
having to change the devices each time.

Acked-by: Eugenio Pérez Martin <eperezma@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
 drivers/vdpa/vdpa_sim/vdpa_sim.h     |  3 ++-
 drivers/vdpa/vdpa_sim/vdpa_sim.c     | 17 +++++++++++++++--
 drivers/vdpa/vdpa_sim/vdpa_sim_blk.c |  6 ++----
 drivers/vdpa/vdpa_sim/vdpa_sim_net.c |  6 ++----
 4 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.h b/drivers/vdpa/vdpa_sim/vdpa_sim.h
index 144858636c10..acee20faaf6a 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.h
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.h
@@ -45,7 +45,7 @@ struct vdpasim_dev_attr {
 	u32 ngroups;
 	u32 nas;
 
-	work_func_t work_fn;
+	void (*work_fn)(struct vdpasim *vdpasim);
 	void (*get_config)(struct vdpasim *vdpasim, void *config);
 	void (*set_config)(struct vdpasim *vdpasim, const void *config);
 	int (*get_stats)(struct vdpasim *vdpasim, u16 idx,
@@ -78,6 +78,7 @@ struct vdpasim {
 
 struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *attr,
 			       const struct vdpa_dev_set_config *config);
+void vdpasim_schedule_work(struct vdpasim *vdpasim);
 
 /* TODO: cross-endian support */
 static inline bool vdpasim_is_little_endian(struct vdpasim *vdpasim)
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index eea23c630f7c..2df5227e0b62 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -127,6 +127,13 @@ static void vdpasim_do_reset(struct vdpasim *vdpasim)
 static const struct vdpa_config_ops vdpasim_config_ops;
 static const struct vdpa_config_ops vdpasim_batch_config_ops;
 
+static void vdpasim_work_fn(struct work_struct *work)
+{
+	struct vdpasim *vdpasim = container_of(work, struct vdpasim, work);
+
+	vdpasim->dev_attr.work_fn(vdpasim);
+}
+
 struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
 			       const struct vdpa_dev_set_config *config)
 {
@@ -163,7 +170,7 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
 
 	vdpasim = vdpa_to_sim(vdpa);
 	vdpasim->dev_attr = *dev_attr;
-	INIT_WORK(&vdpasim->work, dev_attr->work_fn);
+	INIT_WORK(&vdpasim->work, vdpasim_work_fn);
 	spin_lock_init(&vdpasim->lock);
 	spin_lock_init(&vdpasim->iommu_lock);
 
@@ -214,6 +221,12 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
 }
 EXPORT_SYMBOL_GPL(vdpasim_create);
 
+void vdpasim_schedule_work(struct vdpasim *vdpasim)
+{
+	schedule_work(&vdpasim->work);
+}
+EXPORT_SYMBOL_GPL(vdpasim_schedule_work);
+
 static int vdpasim_set_vq_address(struct vdpa_device *vdpa, u16 idx,
 				  u64 desc_area, u64 driver_area,
 				  u64 device_area)
@@ -248,7 +261,7 @@ static void vdpasim_kick_vq(struct vdpa_device *vdpa, u16 idx)
 	}
 
 	if (vq->ready)
-		schedule_work(&vdpasim->work);
+		vdpasim_schedule_work(vdpasim);
 }
 
 static void vdpasim_set_vq_cb(struct vdpa_device *vdpa, u16 idx,
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
index 5117959bed8a..eb4897c8541e 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
@@ -11,7 +11,6 @@
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/kernel.h>
-#include <linux/sched.h>
 #include <linux/blkdev.h>
 #include <linux/vringh.h>
 #include <linux/vdpa.h>
@@ -286,9 +285,8 @@ static bool vdpasim_blk_handle_req(struct vdpasim *vdpasim,
 	return handled;
 }
 
-static void vdpasim_blk_work(struct work_struct *work)
+static void vdpasim_blk_work(struct vdpasim *vdpasim)
 {
-	struct vdpasim *vdpasim = container_of(work, struct vdpasim, work);
 	bool reschedule = false;
 	int i;
 
@@ -326,7 +324,7 @@ static void vdpasim_blk_work(struct work_struct *work)
 	spin_unlock(&vdpasim->lock);
 
 	if (reschedule)
-		schedule_work(&vdpasim->work);
+		vdpasim_schedule_work(vdpasim);
 }
 
 static void vdpasim_blk_get_config(struct vdpasim *vdpasim, void *config)
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_net.c b/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
index 862f405362de..e61a9ecbfafe 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
@@ -11,7 +11,6 @@
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/kernel.h>
-#include <linux/sched.h>
 #include <linux/etherdevice.h>
 #include <linux/vringh.h>
 #include <linux/vdpa.h>
@@ -192,9 +191,8 @@ static void vdpasim_handle_cvq(struct vdpasim *vdpasim)
 	u64_stats_update_end(&net->cq_stats.syncp);
 }
 
-static void vdpasim_net_work(struct work_struct *work)
+static void vdpasim_net_work(struct vdpasim *vdpasim)
 {
-	struct vdpasim *vdpasim = container_of(work, struct vdpasim, work);
 	struct vdpasim_virtqueue *txq = &vdpasim->vqs[1];
 	struct vdpasim_virtqueue *rxq = &vdpasim->vqs[0];
 	struct vdpasim_net *net = sim_to_net(vdpasim);
@@ -260,7 +258,7 @@ static void vdpasim_net_work(struct work_struct *work)
 		vdpasim_net_complete(rxq, write);
 
 		if (tx_pkts > 4) {
-			schedule_work(&vdpasim->work);
+			vdpasim_schedule_work(vdpasim);
 			goto out;
 		}
 	}
-- 
2.39.2


[-- Attachment #2: Type: text/plain, Size: 183 bytes --]

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[PATCH v4 7/9] vdpa_sim: use kthread worker

[Stefano Garzarella]

Let's use our own kthread to run device jobs.
This allows us more flexibility, especially we can attach the kthread
to the user address space when vDPA uses user's VA.

Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---

Notes:
    v3:
    - fix `dev` not initialized in the error path [Simon Horman]

 drivers/vdpa/vdpa_sim/vdpa_sim.h |  3 ++-
 drivers/vdpa/vdpa_sim/vdpa_sim.c | 19 +++++++++++++------
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.h b/drivers/vdpa/vdpa_sim/vdpa_sim.h
index acee20faaf6a..ce83f9130a5d 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.h
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.h
@@ -57,7 +57,8 @@ struct vdpasim_dev_attr {
 struct vdpasim {
 	struct vdpa_device vdpa;
 	struct vdpasim_virtqueue *vqs;
-	struct work_struct work;
+	struct kthread_worker *worker;
+	struct kthread_work work;
 	struct vdpasim_dev_attr dev_attr;
 	/* spinlock to synchronize virtqueue state */
 	spinlock_t lock;
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index 2df5227e0b62..bd9f9054de94 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -11,8 +11,8 @@
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/kernel.h>
+#include <linux/kthread.h>
 #include <linux/slab.h>
-#include <linux/sched.h>
 #include <linux/dma-map-ops.h>
 #include <linux/vringh.h>
 #include <linux/vdpa.h>
@@ -127,7 +127,7 @@ static void vdpasim_do_reset(struct vdpasim *vdpasim)
 static const struct vdpa_config_ops vdpasim_config_ops;
 static const struct vdpa_config_ops vdpasim_batch_config_ops;
 
-static void vdpasim_work_fn(struct work_struct *work)
+static void vdpasim_work_fn(struct kthread_work *work)
 {
 	struct vdpasim *vdpasim = container_of(work, struct vdpasim, work);
 
@@ -170,11 +170,17 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
 
 	vdpasim = vdpa_to_sim(vdpa);
 	vdpasim->dev_attr = *dev_attr;
-	INIT_WORK(&vdpasim->work, vdpasim_work_fn);
+	dev = &vdpasim->vdpa.dev;
+
+	kthread_init_work(&vdpasim->work, vdpasim_work_fn);
+	vdpasim->worker = kthread_create_worker(0, "vDPA sim worker: %s",
+						dev_attr->name);
+	if (IS_ERR(vdpasim->worker))
+		goto err_iommu;
+
 	spin_lock_init(&vdpasim->lock);
 	spin_lock_init(&vdpasim->iommu_lock);
 
-	dev = &vdpasim->vdpa.dev;
 	dev->dma_mask = &dev->coherent_dma_mask;
 	if (dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)))
 		goto err_iommu;
@@ -223,7 +229,7 @@ EXPORT_SYMBOL_GPL(vdpasim_create);
 
 void vdpasim_schedule_work(struct vdpasim *vdpasim)
 {
-	schedule_work(&vdpasim->work);
+	kthread_queue_work(vdpasim->worker, &vdpasim->work);
 }
 EXPORT_SYMBOL_GPL(vdpasim_schedule_work);
 
@@ -623,7 +629,8 @@ static void vdpasim_free(struct vdpa_device *vdpa)
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 	int i;
 
-	cancel_work_sync(&vdpasim->work);
+	kthread_cancel_work_sync(&vdpasim->work);
+	kthread_destroy_worker(vdpasim->worker);
 
 	for (i = 0; i < vdpasim->dev_attr.nvqs; i++) {
 		vringh_kiov_cleanup(&vdpasim->vqs[i].out_iov);
-- 
2.39.2

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[PATCH v4 8/9] vdpa_sim: replace the spinlock with a mutex to protect the state

[Stefano Garzarella]

The spinlock we use to protect the state of the simulator is sometimes
held for a long time (for example, when devices handle requests).

This also prevents us from calling functions that might sleep (such as
kthread_flush_work() in the next patch), and thus having to release
and retake the lock.

For these reasons, let's replace the spinlock with a mutex that gives
us more flexibility.

Suggested-by: Jason Wang <jasowang@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
 drivers/vdpa/vdpa_sim/vdpa_sim.h     |  4 ++--
 drivers/vdpa/vdpa_sim/vdpa_sim.c     | 34 ++++++++++++++--------------
 drivers/vdpa/vdpa_sim/vdpa_sim_blk.c |  4 ++--
 drivers/vdpa/vdpa_sim/vdpa_sim_net.c |  4 ++--
 4 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.h b/drivers/vdpa/vdpa_sim/vdpa_sim.h
index ce83f9130a5d..4774292fba8c 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.h
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.h
@@ -60,8 +60,8 @@ struct vdpasim {
 	struct kthread_worker *worker;
 	struct kthread_work work;
 	struct vdpasim_dev_attr dev_attr;
-	/* spinlock to synchronize virtqueue state */
-	spinlock_t lock;
+	/* mutex to synchronize virtqueue state */
+	struct mutex mutex;
 	/* virtio config according to device type */
 	void *config;
 	struct vhost_iotlb *iommu;
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index bd9f9054de94..2b2e439a66f7 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -178,7 +178,7 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
 	if (IS_ERR(vdpasim->worker))
 		goto err_iommu;
 
-	spin_lock_init(&vdpasim->lock);
+	mutex_init(&vdpasim->mutex);
 	spin_lock_init(&vdpasim->iommu_lock);
 
 	dev->dma_mask = &dev->coherent_dma_mask;
@@ -286,13 +286,13 @@ static void vdpasim_set_vq_ready(struct vdpa_device *vdpa, u16 idx, bool ready)
 	struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
 	bool old_ready;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	old_ready = vq->ready;
 	vq->ready = ready;
 	if (vq->ready && !old_ready) {
 		vdpasim_queue_ready(vdpasim, idx);
 	}
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 }
 
 static bool vdpasim_get_vq_ready(struct vdpa_device *vdpa, u16 idx)
@@ -310,9 +310,9 @@ static int vdpasim_set_vq_state(struct vdpa_device *vdpa, u16 idx,
 	struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
 	struct vringh *vrh = &vq->vring;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	vrh->last_avail_idx = state->split.avail_index;
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return 0;
 }
@@ -409,9 +409,9 @@ static u8 vdpasim_get_status(struct vdpa_device *vdpa)
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 	u8 status;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	status = vdpasim->status;
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return status;
 }
@@ -420,19 +420,19 @@ static void vdpasim_set_status(struct vdpa_device *vdpa, u8 status)
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	vdpasim->status = status;
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 }
 
 static int vdpasim_reset(struct vdpa_device *vdpa)
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	vdpasim->status = 0;
 	vdpasim_do_reset(vdpasim);
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return 0;
 }
@@ -441,9 +441,9 @@ static int vdpasim_suspend(struct vdpa_device *vdpa)
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	vdpasim->running = false;
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return 0;
 }
@@ -453,7 +453,7 @@ static int vdpasim_resume(struct vdpa_device *vdpa)
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 	int i;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	vdpasim->running = true;
 
 	if (vdpasim->pending_kick) {
@@ -464,7 +464,7 @@ static int vdpasim_resume(struct vdpa_device *vdpa)
 		vdpasim->pending_kick = false;
 	}
 
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return 0;
 }
@@ -536,14 +536,14 @@ static int vdpasim_set_group_asid(struct vdpa_device *vdpa, unsigned int group,
 
 	iommu = &vdpasim->iommu[asid];
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 
 	for (i = 0; i < vdpasim->dev_attr.nvqs; i++)
 		if (vdpasim_get_vq_group(vdpa, i) == group)
 			vringh_set_iotlb(&vdpasim->vqs[i].vring, iommu,
 					 &vdpasim->iommu_lock);
 
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return 0;
 }
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
index eb4897c8541e..568119e1553f 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
@@ -290,7 +290,7 @@ static void vdpasim_blk_work(struct vdpasim *vdpasim)
 	bool reschedule = false;
 	int i;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 
 	if (!(vdpasim->status & VIRTIO_CONFIG_S_DRIVER_OK))
 		goto out;
@@ -321,7 +321,7 @@ static void vdpasim_blk_work(struct vdpasim *vdpasim)
 		}
 	}
 out:
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	if (reschedule)
 		vdpasim_schedule_work(vdpasim);
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_net.c b/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
index e61a9ecbfafe..7ab434592bfe 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
@@ -201,7 +201,7 @@ static void vdpasim_net_work(struct vdpasim *vdpasim)
 	u64 rx_drops = 0, rx_overruns = 0, rx_errors = 0, tx_errors = 0;
 	int err;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 
 	if (!vdpasim->running)
 		goto out;
@@ -264,7 +264,7 @@ static void vdpasim_net_work(struct vdpasim *vdpasim)
 	}
 
 out:
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	u64_stats_update_begin(&net->tx_stats.syncp);
 	net->tx_stats.pkts += tx_pkts;
-- 
2.39.2

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[PATCH v4 9/9] vdpa_sim: add support for user VA

[Stefano Garzarella]

The new "use_va" module parameter (default: true) is used in
vdpa_alloc_device() to inform the vDPA framework that the device
supports VA.

vringh is initialized to use VA only when "use_va" is true and the
user's mm has been bound. So, only when the bus supports user VA
(e.g. vhost-vdpa).

vdpasim_mm_work_fn work is used to serialize the binding to a new
address space when the .bind_mm callback is invoked, and unbinding
when the .unbind_mm callback is invoked.

Call mmget_not_zero()/kthread_use_mm() inside the worker function
to pin the address space only as long as needed, following the
documentation of mmget() in include/linux/sched/mm.h:

  * Never use this function to pin this address space for an
  * unbounded/indefinite amount of time.

Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---

Notes:
    v4:
    - checked `use_va` in vdpasim_work_fn() [Jason]
    - removed `va_enabled` variable now used only in the if condition
    v3:
    - called mmget_not_zero() before kthread_use_mm() [Jason]
      As the documentation of mmget() in include/linux/sched/mm.h says:
    
      * Never use this function to pin this address space for an
      * unbounded/indefinite amount of time.
    
      I moved mmget_not_zero/kthread_use_mm inside the worker function,
      this way we pin the address space only as long as needed.
      This is similar to what vfio_iommu_type1_dma_rw_chunk() does in
      drivers/vfio/vfio_iommu_type1.c
    - simplified the mm bind/unbind [Jason]
    - renamed vdpasim_worker_change_mm_sync() [Jason]
    - fix commit message (s/default: false/default: true)
    v2:
    - `use_va` set to true by default [Eugenio]
    - supported the new unbind_mm callback [Jason]
    - removed the unbind_mm call in vdpasim_do_reset() [Jason]
    - avoided to release the lock while call kthread_flush_work() since we
      are now using a mutex to protect the device state

 drivers/vdpa/vdpa_sim/vdpa_sim.h |  1 +
 drivers/vdpa/vdpa_sim/vdpa_sim.c | 97 +++++++++++++++++++++++++++++---
 2 files changed, 90 insertions(+), 8 deletions(-)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.h b/drivers/vdpa/vdpa_sim/vdpa_sim.h
index 4774292fba8c..3a42887d05d9 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.h
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.h
@@ -59,6 +59,7 @@ struct vdpasim {
 	struct vdpasim_virtqueue *vqs;
 	struct kthread_worker *worker;
 	struct kthread_work work;
+	struct mm_struct *mm_bound;
 	struct vdpasim_dev_attr dev_attr;
 	/* mutex to synchronize virtqueue state */
 	struct mutex mutex;
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index 2b2e439a66f7..2c706bb18897 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -35,10 +35,44 @@ module_param(max_iotlb_entries, int, 0444);
 MODULE_PARM_DESC(max_iotlb_entries,
 		 "Maximum number of iotlb entries for each address space. 0 means unlimited. (default: 2048)");
 
+static bool use_va = true;
+module_param(use_va, bool, 0444);
+MODULE_PARM_DESC(use_va, "Enable/disable the device's ability to use VA");
+
 #define VDPASIM_QUEUE_ALIGN PAGE_SIZE
 #define VDPASIM_QUEUE_MAX 256
 #define VDPASIM_VENDOR_ID 0
 
+struct vdpasim_mm_work {
+	struct kthread_work work;
+	struct vdpasim *vdpasim;
+	struct mm_struct *mm_to_bind;
+	int ret;
+};
+
+static void vdpasim_mm_work_fn(struct kthread_work *work)
+{
+	struct vdpasim_mm_work *mm_work =
+		container_of(work, struct vdpasim_mm_work, work);
+	struct vdpasim *vdpasim = mm_work->vdpasim;
+
+	mm_work->ret = 0;
+
+	//TODO: should we attach the cgroup of the mm owner?
+	vdpasim->mm_bound = mm_work->mm_to_bind;
+}
+
+static void vdpasim_worker_change_mm_sync(struct vdpasim *vdpasim,
+					  struct vdpasim_mm_work *mm_work)
+{
+	struct kthread_work *work = &mm_work->work;
+
+	kthread_init_work(work, vdpasim_mm_work_fn);
+	kthread_queue_work(vdpasim->worker, work);
+
+	kthread_flush_work(work);
+}
+
 static struct vdpasim *vdpa_to_sim(struct vdpa_device *vdpa)
 {
 	return container_of(vdpa, struct vdpasim, vdpa);
@@ -59,13 +93,20 @@ static void vdpasim_queue_ready(struct vdpasim *vdpasim, unsigned int idx)
 {
 	struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
 	uint16_t last_avail_idx = vq->vring.last_avail_idx;
-
-	vringh_init_iotlb(&vq->vring, vdpasim->features, vq->num, true,
-			  (struct vring_desc *)(uintptr_t)vq->desc_addr,
-			  (struct vring_avail *)
-			  (uintptr_t)vq->driver_addr,
-			  (struct vring_used *)
-			  (uintptr_t)vq->device_addr);
+	struct vring_desc *desc = (struct vring_desc *)
+				  (uintptr_t)vq->desc_addr;
+	struct vring_avail *avail = (struct vring_avail *)
+				    (uintptr_t)vq->driver_addr;
+	struct vring_used *used = (struct vring_used *)
+				  (uintptr_t)vq->device_addr;
+
+	if (use_va && vdpasim->mm_bound) {
+		vringh_init_iotlb_va(&vq->vring, vdpasim->features, vq->num,
+				     true, desc, avail, used);
+	} else {
+		vringh_init_iotlb(&vq->vring, vdpasim->features, vq->num,
+				  true, desc, avail, used);
+	}
 
 	vq->vring.last_avail_idx = last_avail_idx;
 
@@ -130,8 +171,20 @@ static const struct vdpa_config_ops vdpasim_batch_config_ops;
 static void vdpasim_work_fn(struct kthread_work *work)
 {
 	struct vdpasim *vdpasim = container_of(work, struct vdpasim, work);
+	struct mm_struct *mm = vdpasim->mm_bound;
+
+	if (use_va && mm) {
+		if (!mmget_not_zero(mm))
+			return;
+		kthread_use_mm(mm);
+	}
 
 	vdpasim->dev_attr.work_fn(vdpasim);
+
+	if (use_va && mm) {
+		kthread_unuse_mm(mm);
+		mmput(mm);
+	}
 }
 
 struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
@@ -162,7 +215,7 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
 	vdpa = __vdpa_alloc_device(NULL, ops,
 				   dev_attr->ngroups, dev_attr->nas,
 				   dev_attr->alloc_size,
-				   dev_attr->name, false);
+				   dev_attr->name, use_va);
 	if (IS_ERR(vdpa)) {
 		ret = PTR_ERR(vdpa);
 		goto err_alloc;
@@ -582,6 +635,30 @@ static int vdpasim_set_map(struct vdpa_device *vdpa, unsigned int asid,
 	return ret;
 }
 
+static int vdpasim_bind_mm(struct vdpa_device *vdpa, struct mm_struct *mm)
+{
+	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
+	struct vdpasim_mm_work mm_work;
+
+	mm_work.vdpasim = vdpasim;
+	mm_work.mm_to_bind = mm;
+
+	vdpasim_worker_change_mm_sync(vdpasim, &mm_work);
+
+	return mm_work.ret;
+}
+
+static void vdpasim_unbind_mm(struct vdpa_device *vdpa)
+{
+	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
+	struct vdpasim_mm_work mm_work;
+
+	mm_work.vdpasim = vdpasim;
+	mm_work.mm_to_bind = NULL;
+
+	vdpasim_worker_change_mm_sync(vdpasim, &mm_work);
+}
+
 static int vdpasim_dma_map(struct vdpa_device *vdpa, unsigned int asid,
 			   u64 iova, u64 size,
 			   u64 pa, u32 perm, void *opaque)
@@ -678,6 +755,8 @@ static const struct vdpa_config_ops vdpasim_config_ops = {
 	.set_group_asid         = vdpasim_set_group_asid,
 	.dma_map                = vdpasim_dma_map,
 	.dma_unmap              = vdpasim_dma_unmap,
+	.bind_mm		= vdpasim_bind_mm,
+	.unbind_mm		= vdpasim_unbind_mm,
 	.free                   = vdpasim_free,
 };
 
@@ -712,6 +791,8 @@ static const struct vdpa_config_ops vdpasim_batch_config_ops = {
 	.get_iova_range         = vdpasim_get_iova_range,
 	.set_group_asid         = vdpasim_set_group_asid,
 	.set_map                = vdpasim_set_map,
+	.bind_mm		= vdpasim_bind_mm,
+	.unbind_mm		= vdpasim_unbind_mm,
 	.free                   = vdpasim_free,
 };
 
-- 
2.39.2

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